Matter and change
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  • Substance – matter that has uniform and unchanging composition (pure substance) – table salt, water, sea water Physical properties – observed and measured without changing the composition – density, color, odor, taste, hardness, melting point, boiling point Chemical Properties – Ability of a substance to combine with or change into one or more other substances – iron rust, reactions.
  • Solute can differ. Solvent is usually water.
  • Table salt, water, sugar, aspirin. 10 million known compounds. Medicines.
  • Distinctly different properties – water and peroxide
  • Atomic Number – number of protons in an atom. On top. Atomic Mass – number on bottom.

Matter and change Presentation Transcript

  • 1. Matter andChange P Squires General Chemistry 2005-2006
  • 2. Observing Chemical Change• Open book to page 55 and conduct Discovery Lab • (50 pts)
  • 3. Properties of Matter•What is a substance?• Physical Properties• Chemical Properties
  • 4. Physical StatesSolid What are some Liquid characteristics of each? Gas Plasma
  • 5. Give the physical state of each of these: 1. Silver Solid 2. Gasoline Liquid 3. Helium Gas 4. Rubbing alcohol Liquid 5. Air Gas 6. Glass Solid or liquid 7. Lightning Plasma
  • 6. Plasma
  • 7. Physical Changes • Physical changes only involve changes in state or appearance.• What are some examples of physical change?
  • 8. Catch words for Physical Change• Boil •Split• Freeze •Grind• Melt •Cut• Condense •Crush• Break •Bend
  • 9. Chemical Changes• Chemical changes and chemical properties always produce new substances.
  • 10. Chemical or physical change ???• Food spoiling Chemical• Nail rusting Chemical• Oil burning Chemical• Sugar dissolving Physical• Water boiling Physical• Firefly flashing Chemical• Egg cooking Chemical• Snowflake melting Physical
  • 11. Percent massPercent mass (%) = mass of element_ x 100 mass of compound
  • 12. Calculations1. A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound?2. If 1.0 g of hydrogen reacts completely with 19.0 g of fluorine, what is the percent by mass of hydrogen in the compound that is formed?
  • 13. Pure Substances• Elements are the building blocks of matter.• Atoms are the smallest part of an element.
  • 14. Mixtures… do not have a definite composition… are either heterogeneous,with clearly visible components… or homogeneous, which are uniform in appearance
  • 15. Solutions• Solutions are homogeneous mixtures containing a solute which is dissolved in a solvent.
  • 16. Classify as heterogeneous, or homogeneous (solution)• Blood Homogeneous• Choc. chip ice cream Heterogeneous• Brass (Cu-Zn alloy) Homogeneous• Homogenized milk Homogeneous• Hummingbird food Homogeneous (solution)
  • 17. We separate mixtures …… based on differences in the chemical and physicalproperties of the components in the mixture.
  • 18. Separating Mixtures• Quick Lab Handout• (50 points)
  • 19. How would you separate the following?Aluminum filings and iron filings? Saw dust and sand? Salt and powdered charcoal? Water and alcohol?
  • 20. Elements• A pure substance that can not be separated into simpler substance by physical or chemical means.
  • 21. Compounds• A combination of two or more different elements that are combined chemically.• What are some examples of compounds?
  • 22. The Law of Conservation of MassMatter can neither be created or destroyed during a chemical reaction.
  • 23. Law of Definite Proportions Elements comprisecompounds in definite proportions by mass.
  • 24. Law of Multiple Proportions When different compounds are formed, they combine in whole number ratios. H2O H2O2
  • 25. ChemLab• Read and complete ChemLab page 78. (100 points) • Answer Questions at end: Analyze and Conclude.
  • 26. Structure of the Atom
  • 27. Part of the Atom• Electron• Proton What charge does each have?• Neutron Where are they found? Which ones make up the mass of the atom? Which ones make up the size of the atom?
  • 28. How Do Atoms Differ? •Atomic Number •Atomic Mass
  • 29. Element Atomic Protons Electrons Atomic Number Mass He 2 Pb 82 8 30
  • 30. Mass Number Number of neutrons =mass number – atomic number
  • 31. Isotopes ……of the same element have thesame number of protons andelectrons but different numbers ofneutrons. Therefore, isotopes of the same element have different masses.
  • 32. Symbols for Isotopes Mass numberA is the A Symbol Esymbolfor mass Z of Elementnumber Z is the symbol for Atomic number atomic number
  • 33. MiniLab• Do modeling isotope lab on page 102.
  • 34. Energy andElectrons
  • 35. Light and Energy• Frequency = f or f with units of Hertz (Hz)• Wavelength = λ with units of meters (m)
  • 36. What is the relationshipbetween frequency and wavelength?
  • 37. For electromagneticenergy, the equation is: c = fλ c is the speed of light c = 3.00 x 10 m/sec 8
  • 38. Electromagnetic Spectrum• Electromagnetic waves carry energy. • Light is part of theelectromagnetic spectrum
  • 39. The Electromagnetic Spectrumgamma rays microwaves visible light ultraviolet infraredX-rays radar radio TV Shorter wavelength Longer wavelength Higher frequency Lower frequency Higher energy Lower energy
  • 40. gamma rays X-rays 400 nm ultraviolet visible light infrared microwavesIncreasing energy radar TV 700 nm radio The Electromagnetic Spectrum
  • 41. The visible spectrum wasdiscovered by … Dr. Roy G. BivRed Orange Yellow Green Blue Indigo Violet 700 nm 400 nm Lower energy Higher energy
  • 42. Niels BohrBohr said that electrons could exist only in certain discrete energy levels … … and that electrons can only change energy levels when they absorb or give off a certain amount of energy. (1913)
  • 43. Hydrogen atomDiscrete energy levels for electronselectron nucleus
  • 44. Hydrogen atomElectrons can exist in this orbit,
  • 45. Hydrogen atom…or in this orbit,
  • 46. Hydrogen atom…or inthis orbit,
  • 47. Hydrogen atom…but not in between the orbits.
  • 48. Hydrogen atomUnless the electron isabsorbing energy, or …Giving off energy
  • 49. When high voltage is connected to the hydrogen discharge tube, a bluish light is given off.When observed through a diffraction grating, specific lines of color are observed.
  • 50. The electron in a hydrogen atom gains energy from the electricity passing thru the tube and …… the electron moves up to a higher energy level.
  • 51. The electron in the excited state is “unstable”.The electron drops to a lower energy level, and …… gives off light of a certain energy and wavelength.
  • 52. Hydrogen atom
  • 53. HydrogenThe electronabsorbs atomenergy and … ener g y
  • 54. Hydrogen atom …the electron is elevated to the nextenergy level
  • 55. Hydrogen atom The electron is unstable and “wants” toreturn to a lower energy level
  • 56. Hydrogen atomLight of aparticularwavelengthis given off
  • 57. Helium
  • 58. Neon
  • 59. Hydrogen
  • 60. “Regardless of it’s shortcomings and themodifications that were laterapplied, Bohr’s model of the atom was the firstsuccessful attempt to makethe internal structure of the atom agree with spectroscopic data.” Asimov, 1964
  • 61. QuantumMechanical Model of the Atom1. A small, dense positively charged nucleus which contains protons and neutrons.2. Electrons which exist outside of the nucleus at … – various distances from the nucleus, and at … – various energy levels.
  • 62. The Electrons3. The electrons can have both a mass, as does matter, and a wavelength, as does light energy.4. The electrons themselves are not little solid spheres in orbit around the nucleus, but exist as a “fog” of half- energy, half-matter. The electrons can behave as either matter or energy, depending on the experiment.
  • 63. Energy Levels5. Based on the ideas of Bohr, the electrons are located … – … in major energy levels, – … in energy sublevels within major energy levels, – … in orbitals within each sublevel.
  • 64. Next up….The Periodic Table